JPH10138318A - Production of multilayered extrusion polyimide film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform the lamination with metal foil under a relatively gentle condition by using a polyamic acid soln. forming substrate polyimide having an imide unit represented by specific formula and using a soln. of polyimide having a specific compsn. composed of an imide unit represented by a specific formula or a precursor thereof. SOLUTION: An a polyamic acid soln. for a substrate layer, a polyamic acid soln. forming substrate polyimide having an imide unit represented by formula I is used. As a soln. of polyimide for a thin layer or a precursor thereof, a soln. of polyimide consisting of imide units A, B represented by formulae II, III (wherein R is a tetravalent aromatic residue and R' is a divalent aromatic or aliphatic residue) and characterized by that A is 80-100mol% and B is 20-0mol%) or a precursor thereof is used. These solns. are extruded to a support to form a solvent-containing multilayered extrudate which is, in turn, heated and dried to be imidated to obtain a multilayered polyimide film low in the coefficient of thermal and linear expansion.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a multilayer extruded polyimide film, and more particularly to a method for producing a polyimide film having a low linear thermal expansion.
A multilayer extruded polyimide film comprising a specific polyimide layer laminated on one or both sides of a base polyimide layer containing 4'-biphenyltetracarboxylic dianhydride and paraphenylenediamine as essential components by a multilayer extrusion casting method. It relates to the manufacturing method.

[0002]

2. Description of the Related Art Aromatic polyimide films are widely used for electronic devices such as cameras, personal computers, and liquid crystal displays. In order to use an aromatic polyimide film as a substrate material for a flexible printed board (FPC) or a tape-automated bonding (TAB), a copper foil is laminated using an adhesive such as an epoxy resin. The method has been adopted.

It has been pointed out that aromatic polyimide films are excellent in heat resistance, mechanical strength, electrical properties and the like, but are inferior in properties of polyimide due to poor heat resistance of adhesives. To solve such a problem,
An all-polyimide substrate has been developed in which copper is electroplated on a polyimide film without using an adhesive, a polyamic acid solution is applied to a copper foil, dried and imidized, or a thermoplastic polyimide is thermocompressed. ing.

Further, a polyimide laminate in which a polyimide adhesive is sandwiched between a polyimide film and a metal foil and a method for producing the same are known (US Pat. No. 4,543,295). However, this polyimide laminate and its production method cannot be used for a polyimide film containing 3,3 ', 4,4'-biphenyltetracarboxylic acid and paraphenylenediamine as essential components because the peel strength from the metal foil is small. There is a problem.

Further, a multilayer aromatic polyimide film, a metal foil laminated polyimide film and a method for producing the same are known (Japanese Patent Application Laid-Open Nos. 3-180343 and 4-33).
847, JP-A-4-33848). However, these methods require an epoxy-based adhesive or a relatively high temperature and a high pressure to directly bond the metal foil and the multilayer polyimide film to each other.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing a multilayer polyimide film which can be laminated with a metal foil under relatively mild conditions and has a small coefficient of linear thermal expansion.

[0007]

That is, the present invention provides:
Multilayer extrusion flow combining a polyamic acid solution for the base layer and a solution of polyimide or its precursor for the thin layer with an extruder having two or three layers of extrusion dies and a solution casting film forming apparatus In a method for producing a multilayer extruded polyimide film by a cast film forming method, a polyamic acid solution giving a substrate polyimide (X) having an imide unit of the following formula is used as a polyamic acid solution for a substrate layer,

Embedded image As a solution of polyimide or a precursor thereof for a thin layer, the imide unit comprises the following imide units (A) and (B),

Embedded image [In the formula (B), R represents a tetravalent aromatic residue, and R ′ represents a divalent aromatic or aliphatic residue. (A) is 80 to 100 mol%, and (B) is 20 to 0 mol%.
A multi-layer extrudate containing a solvent extruded on a support is heated and dried and imidized using a solution of polyimide (Y) or a precursor thereof, which has a coefficient of linear thermal expansion of 5 × 10 ^{− The present invention} relates to a method for producing a multilayer extruded polyimide film having a temperature of 6-30 × 10 ⁻⁶ cm / cm / ° C.

The base polyimide (X) according to the present invention
Are 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (hereinafter sometimes abbreviated simply as s-BPDA) and paraphenylenediamine (hereinafter sometimes simply abbreviated as PPD). In some cases, it is further produced from 4,4′-diaminodiphenyl ether (hereinafter may be simply abbreviated as DADE). PPD / DADE
(Molar ratio) needs to be 100/0 to 70/30. In the synthesis of the base polyimide (X), if the proportion of each component is finally within the above range, random polymerization, block polymerization, or synthesis of two kinds of polyamic acids in advance, mixing of both polyamic acid solutions, and reaction conditions This is achieved by any of the methods of mixing below. By setting the proportion of each component within the above range, the finally obtained flexible multilayer extruded polyimide film has excellent properties, particularly a small coefficient of linear thermal expansion, good heat resistance,
Shows mechanical and electrical properties.

Using each of the above components, a substantially equimolar amount of a diamine component and a tetracarboxylic dianhydride are reacted in an organic solvent to form a solution of a polyamic acid (partly if a uniform solution state is maintained). May be imidized).
Using other types and amounts of aromatic tetracarboxylic dianhydrides such as pyromellitic dianhydride, aromatic diamines such as 4,4'-diaminodiphenylmethane etc. which do not impair the physical properties of the polyimide (X) You may.

In the present invention, the polyimide (Y) is
1,3-bis (4-aminophenoxy) benzene (hereinafter sometimes abbreviated simply as TPE-R), 2,3,
A 3 ′, 4′-biphenyltetracarboxylic dianhydride (hereinafter sometimes simply referred to as a-BPDA) component;
It is optionally produced from other tetracarboxylic dianhydrides and diamine components. Using each of the above components, preferably, a tetraamic dianhydride is reacted in an organic solvent under excess conditions or under conditions in which diamine terminals are blocked with a dicarboxylic anhydride, and a solution of a polyamic acid ( Some may be imidized as long as a uniform solution state is maintained).

The polyimide (Y) is 2,3,
3 ′, 4′-biphenyltetracarboxylic dianhydride, 1,3-bis (4-aminophenoxy) benzene, and optionally another tetracarboxylic dianhydride and another diamine in an organic solvent, About 100 ° C or less, especially 2
The solution is reacted at a temperature of 0 to 60 ° C. to form a solution of polyamic acid, and the solution of polyamic acid is used as a dope solution, a thin film of the dope solution is formed, and the solvent is evaporated from the thin film and removed. Together with the imide cyclization of a polyamic acid.

Further, the solution of the polyamic acid prepared as described above is heated to 150 to 250 ° C. or 150 ° C. or less, particularly 15 to 50 ° C. by adding an imidizing agent.
And then evaporating the solvent after imide cyclization, or precipitating in a poor solvent to form a powder, and dissolving the powder in an organic solution to obtain an organic solvent solution of polyimide (Y). Can be.

The tetracarboxylic dianhydride which can be used for the polyimide (Y) in the present invention includes 2,2
Most preferred is 3,3 ′, 4′-biphenyltetracarboxylic dianhydride, but not more than 20 mol%, preferably 1%.
0% by mole or less of another aromatic tetracarboxylic dianhydride (in the above formula, a tetracarboxylic dianhydride containing an R group),
For example, pyromellitic dianhydride, 3,3 ', 4,4'
-Benzophenonetetracarboxylic dianhydride, 3,
3 ', 4,4'-biphenyltetracarboxylic dianhydride, 2,2-bis (3,4-dicarboxyphenyl) propane dianhydride, bis (3,4-dicarboxyphenyl) ether dianhydride , Bis (3,4-dicarboxyphenyl) sulfone dianhydride or 2,3,6,7-naphthalenetetracarboxylic dianhydride.
It may be replaced by 3 ', 4,4'-biphenyltetracarboxylic dianhydride.

As the diamine which can be used for the polyimide (Y) in the present invention, 1,3-bis (4-aminophenoxy) benzene is most preferable, but preferably 20 mol% or less, particularly 10 mol% or less. Is another diamine (diamine containing an R ′ group in the above formula), for example, 4,
4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfide, 4,4'-diaminobenzophenone, 4,4'-diaminodiphenylmethane, 2,2
-Bis (4-aminophenyl) propane, 1,4-bis (4-aminophenoxy) benzene, 4,4'-bis (4-aminophenyl) diphenyl ether, 4,4 '
-Bis (4-aminophenyl) diphenyl sulfone,
4,4'-bis (4-aminophenyl) diphenyl sulfide, 4,4'-bis (4-aminophenyl) diphenylmethane, 4,4'-bis (4-aminophenoxy)
Diphenyl ether, 4,4'-bis (4-aminophenoxy) diphenyl sulfone, 4,4'-bis (4-aminophenoxy) diphenyl sulfide, 4,4'-bis (4-aminophenoxy) diphenylmethane, , 2
Flexible aromatic diamines having a plurality of benzene rings, such as -bis [4- (aminophenoxy) phenyl] propane and 2,2-bis [4- (4-aminophenoxy) phenyl] hexafluoropropane; It may be replaced by an aliphatic diamine such as diaminobutane, 1,6-diaminohexane, 1,8-diaminooctane, 1,10-diaminodecane, 1,12-diaminododecane, or a diamine such as xylenediamine. The use ratio of the flexible aromatic diamine having a plurality of benzene rings is preferably 20 mol% or less, particularly preferably 10 mol% or less based on the total diamine. Further, the use ratio of the aliphatic diamine is preferably 20 mol% or less based on the total diamine. Exceeding this ratio lowers the heat resistance of the polyimide (Y).

In the present invention, a dicarboxylic acid anhydride for blocking the amine terminal of the polyimide (Y), for example, phthalic anhydride and its substitution, hexahydrophthalic anhydride and its substitution, succinic anhydride In particular, phthalic anhydride can be used.

In order to obtain the polyimide (Y) in the present invention, the amount of the diamine (as the number of moles of amino group) in the above-mentioned organic solvent is the total number of moles of the acid anhydride (tetraacid dianhydride and dicarboxylic acid). (Total moles of acid anhydride groups as acid anhydride groups)
1.0, especially 0.98 to 1.0, and especially 0.0.
99 to 1.0, and the amount of the dicarboxylic anhydride to be used is preferably 0.05 or less, more preferably 0.0001 to less, as the ratio to the molar amount of the acid anhydride group of the tetracarboxylic dianhydride.
It is preferable to react each component at a ratio of 0.02.

If the use ratio of the diamine and dicarboxylic anhydride is out of the above range, the molecular weight of the obtained polyamic acid, that is, polyimide (Y) is small, and the strength of the film and the peel strength are lowered. Also,
In particular, under the condition of an excess of the diamine component, cyclization imidization of the polyamic acid or deterioration occurs when the solvent is removed, and the like.
This results in a decrease in physical properties of the film and a decrease in peel strength.
For the purpose of restricting the gelation, a phosphorus-based stabilizer such as triphenyl phosphite, triphenyl phosphate or the like is added at a concentration of 0.2 to the solid content (polymer) concentration at the time of polyamic acid polymerization.
It can be added in the range of 01 to 1%.

The organic solvent used for the production of the polyamic acid is N-methyl-2-pyrrolidone, N, N
-Dimethylformamide, N, N-dimethylacetamide, N, N-diethylacetamide, dimethylsulfoxide, hexamethylphosphoramide, N-methylcaprolactam, cresols and the like. These organic solvents may be used alone or in combination of two or more.

In the production of the multilayer polyimide film according to the present invention, for example, the base polyimide (X)
Co-extrusion of a polyamic acid solution (a transparent viscous solution) and a solution of a polyimide (Y) or a precursor thereof for a thin layer,
It is preferably applied by casting onto a support such as a stainless steel mirror surface or a belt surface, and is preferably in a semi-cured state at 100 to 200 ° C. or a dried state before that. Treating a cast film at a high temperature exceeding 200 ° C. tends to cause defects such as a decrease in adhesiveness in the production of a multilayer polyimide film. The semi-cured state or a state before the semi-cured state means a self-supporting state which is partially gelled by heating and / or chemical imidization, or has a self-supporting state immediately before.

In the present invention, the substrate polyimide (X)
The coextrusion of a solution of a polyamic acid to give a polyimide and a solution of a polyamic acid or a solution of a polyimide to give a polyimide (Y) is carried out, for example, by a coextrusion method described in JP-A-3-180343. The layer can be supplied to a die for extrusion molding and cast on a support. In the present invention, a polyamic acid solution or a polyimide solution that provides the polyimide (Y) is laminated on one or both surfaces of the extruded material layer that provides the polyimide (X) to form a multi-layered film, and after drying, the polyimide (Y) The glass is heated to a temperature below the temperature at which deterioration occurs at or above the glass transition temperature (Tg), preferably 360 ° C. or less, particularly preferably 310 ° C. to 360 ° C. (surface temperature measured by a surface thermometer). It can be dried (preferably heated at this temperature for 1-60 minutes) and imidized to produce a multilayer extruded polyimide film.

In the present invention, the substrate polyimide (X)
The film (layer) preferably has a thickness of 15 to 150 μm. When the thickness is less than 15 μm, problems occur in mechanical strength and dimensional stability of the formed multilayer polyimide film. On the other hand, when the thickness is more than 150 μm, there are difficulties in removing the solvent and imidizing. In the present invention, the thickness of the flexible polyimide (Y) layer is preferably 2 to 30 μm, particularly preferably 2 to 10 μm. If it is less than 2 μm, the adhesive performance is reduced, and
Although it can be used even if it exceeds, there is no particular effect, but rather the heat resistance of the metal foil laminate decreases. The thickness of the film (layer) of the base polyimide (X) is preferably 70% or more of the entire multilayer film. If it is smaller than this ratio, the coefficient of linear thermal expansion of the multilayer film created will increase,
Problems such as mechanical strength and dimensional stability occur.

In the present invention, curing can be performed at a relatively low temperature by selecting a specific combination of polyimide (X) and polyimide (Y).
The imidization and drying of the multilayer polyimide film can be completed without causing degradation of the polyimide (Y),
As a result, the coefficient of linear thermal expansion is 5 × 10 ⁻⁶ −30 × 10 ⁻⁶ c
m / cm / ° C., preferably 10 × 10 ⁻⁶ −25 × 10 ⁻⁶
It is possible to obtain a laminate having high adhesion strength by adhering to the same kind or different kinds of base materials such as metal foil and ceramic under mild conditions.

The multilayer extruded polyimide film produced by the method of the present invention is prepared by directly applying a base material, for example, a metal foil or an adhesive such as epoxy resin, polyetherimide, polyamide, etc., to one or both surfaces of the polyimide (Y) layer. After being provided, they are overlaid and laminated. In the case of direct lamination, the temperature is preferably 280 to 330 ° C., and 1 to 100 kgf.
/ Cm ² , particularly 30-80 kgf / cm ² , for 1 second to 30 minutes. Further, under the above conditions, the multilayer polyimide film and the metal foil can be produced by a continuous hot melt method using a heat roll.

When the multilayer extruded polyimide film produced by the method of the present invention is used, the peel strength of the laminate is increased without using another adhesive, and when the above-mentioned other adhesive is used in combination, the other It is possible to make the adhesive layer thinner. For this reason, the laminate has less change in shape with respect to heat and pressure, and can be applied to fine processing.

The multilayer polyimide film produced by the method of the present invention is a heat-fusible polyimide film, and may be an FPC, a multilayer FPC, a multilayer printed wiring board,
Metal base substrate, bonding sheet, LOC tape,
Can be used for heat-resistant wires and sheet heating elements.

Depending on these applications, a filler for improving the thermal conductivity, the fusion rate, etc., on any of the polyimide layers of the above-mentioned heat-fusible polyimide film, which is a multilayer polyimide film, such as aluminum nitride, silicon nitride, etc. And a metal oxide such as SiO ₂ may be added.

Examples of the metal foil used for the laminate include various metal foils such as copper, aluminum, gold, and alloy foils, preferably rolled copper and electrolytic copper. The thickness of the metal foil is not particularly limited, but is 10 to 60 μm.
Is preferred.

[0028]

The present invention will be described below in more detail with reference to examples and comparative examples. In each of the following examples, the evaluation of the physical properties of the polyimide film and the peel strength of the laminate with the copper foil were measured according to the following methods. Coefficient of linear thermal expansion: measured at 20-200 ° C, 5 ° C / min (M
D), × ppm / ° C. Tensile strength: ASTM D882 (MD), Kgf / m
m ² elongation: ASTM D882 (MD),% Tensile modulus: ASTM D882 (MD), Kgf /
mm ² Heat shrinkage: JIS C2318,% Dielectric breakdown strength: ASTM D149, KV / 25μ Chemical resistance in 10% caustic soda: The elastic modulus retention after 5 days at 25 ° C. was measured. Peel strength of laminate: Using a hot press maintained at 350 ° C.
An electrolytic copper foil (thickness: 35 μm) was superimposed on the polyimide film, and after preheating for 5 minutes, pressed at a pressure of 60 kgf / cm ² for 1 minute to obtain a copper foil laminate. This laminate was measured for T-peel strength at 50 mm / min.

Synthesis Example 1 of Dope for Production of Substrate Polyimide (X) A reaction vessel equipped with a stirrer and a nitrogen inlet tube was charged with N-methyl-
2-Pyrrolidone was added, and paraphenylenediamine (PPD) and 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (s-BPDA) were further added at 1000: 9.
At a molar ratio of 98, the monomer concentration was 18% (% by weight, the same applies hereinafter). After completion of the addition, the reaction was continued for 3 hours while maintaining the temperature at 50 ° C. The obtained polyamic acid solution is a brown viscous liquid, and the solution viscosity at 25 ° C. is about 15
It was 00 poise. This solution (dope) is called X-1.

Synthesis Example 2 of Dope for Producing Substrate Polyimide (X) N, N-dimethylacetamide (DMAC) was added to a reaction vessel equipped with a stirrer and a nitrogen inlet tube, and paraphenylenediamine (PPD) was added. 4,4'-diaminodiphenyl ether and 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride (s-BPDA) were mixed at 850: 1.
It was added so that the monomer concentration became 18% (weight%, the same applies hereinafter) at a molar ratio of 50: 998. 50 ° C after completion of addition
The reaction was continued for 3 hours while maintaining the temperature. The obtained polyamic acid solution was a brown viscous liquid, and the solution viscosity at 25 ° C. was about 1500 poise. This solution (dope) is called X-2.

Synthesis of Dope for Production of Polyimide (Y) for Thin Layer-1 N-methyl-2-pyrrolidone was added to a reaction vessel equipped with a stirrer and a nitrogen inlet tube, and furthermore, 1,3-bis ( 4-
Aminophenoxy) benzene (TPE-R) and 2,3
3 ', 4'-biphenyltetracarboxylic dianhydride (a
-BPDA) and phthalic anhydride at 1000: 995: 1
At a molar ratio of 0, the monomer concentration is 22% and triphenyl phosphate is added at a ratio of 0.2 to the monomer weight.
1% was added. After completion of the addition, the reaction was continued for 1 hour while maintaining the temperature at 25 ° C. To this polyamic acid solution was added 10% of toluene with respect to N-methyl-2-pyrrolidone,
The reaction temperature was raised to 190 ° C., and the reaction was carried out for 5 hours while distilling off generated water together with toluene to obtain a yellow-red viscous polyimide solution. The solution viscosity at 25 ° C. was about 500 poise. This solution (dope) is referred to as Y-1.

Synthesis of Dope for Production of Polyimide (Y) for Thin Layer-2 N, N-dimethylacetamide (DMAC) was added to a reaction vessel equipped with a stirrer and a nitrogen inlet tube.
3-bis (4-aminophenoxy) benzene (TPE-
R), 2,3,3 ′, 4′-biphenyltetracarboxylic dianhydride (a-BPDA) and phthalic anhydride in 100 parts
At a molar ratio of 0: 995: 10, the monomer concentration was 22%, and triphenyl phosphate was added at 0.1% based on the weight of the monomer. After completion of the addition, the reaction was continued at 25 ° C. for 5 hours to obtain a light yellow-brown viscous polyamic acid solution. The solution viscosity at 25 ° C. was about 2000 poise. This solution (dope) is referred to as Y-2.

Synthesis of Dope for Production of Polyimide (Y) -3 N, N-dimethylacetamide (DMAC) was added to a reaction vessel equipped with a stirrer and a nitrogen inlet tube.
3-bis (4-aminophenoxy) benzene (TPE-
R) and 2,3,3 ', 4'-biphenyltetracarboxylic dianhydride (a-BPDA) in a molar ratio of 1000: 1002 so that the monomer concentration becomes 22%, and triphenylphosphonate is used. 0.1% by weight of monomer
added. After the addition was completed, the reaction was continued at 25 ° C. for 4 hours to obtain a light brown transparent viscous polyamic acid solution. The solution viscosity at 25 ° C. was about 1500 poise. This solution (dope) is referred to as Y-3.

[0034]

Example 1 Three-layer extrusion die (multi-manifold
The polyamic acid solution was cast from a three-layer extrusion die onto a metal support using a film forming apparatus equipped with a metal mold (a die), and dried continuously with hot air at 140 ° C. to form a solidified film. . After the solidified film was peeled from the support, the temperature was gradually raised from 200 ° C. to 310 ° C. in a heating furnace to remove the solvent and imidize to produce a long three-layer extruded polyimide film. Table 1 shows the evaluation results of the physical properties of the three-layer extruded polyimide film and the peel strength of the laminate directly laminated with the copper foil.

Example 2-7, Comparative Example 1-3 Using the same apparatus as in Example 1, a multilayer polyimide film or a polyimide film of the type shown in Table 1 was produced under the conditions shown in Table 1. Table 1 shows the physical properties of the obtained polyimide film and the peel strength of the laminate directly laminated with the copper foil.

[0036]

[Table 1]

Example 8 and Comparative Example 4 Using the multilayer polyimide film produced in each example, after providing an epoxy resin layer, the peel strength of a laminate laminated with a copper foil is shown below. Structure of used multilayer polyimide film and thickness of each layer NO. 1: Y-3 / X-2 / Y-3 (4/25/4 μm) NO. 2: Y-3 / X-1 / Y-3 (4/25/4 μm) NO. 3: Y-3 / X-1 / Y-3 (4/50/4 μm) NO. 4: Y-3 / X-1 /-(4/50/0 m) NO. 5: − / X−1 / − (0/25/0 μm) NO. 6: − / X−1 / − (0/50/0 μm)

Epoxy adhesive used: Toray Industries, Inc. TE-5701, thickness: 20-25 μm Adhesion method: An epoxy adhesive (TE) was applied to a copper foil (35 μm).
-5701), and dried at 130 ° C. for 15 minutes.
On top of this, a multilayer polyimide film is overlaid so that the epoxy layer and the Y layer overlap, and 180 ° C., 6.5 kg / cm ² ,
It was pressed for 5 minutes and further heat-treated at 180 ° C. for 1 hour.

Peel strength (T-peel strength) 1: 1.9 kg / cm NO. 2: 2.0 kg / cm or more (film breaks) NO. 3: 1.2 kg / cm NO. 4: 1.1 kg / cm NO. 5: 0.2 kg / cm NO. 6: 0.3 kg / cm It was confirmed that there was substantially no difference between the 90 ° peel strength and the T-peel strength.

[0040]

According to the present invention, the metal foil can be laminated on the metal foil under relatively mild conditions, and the low thermal expansion of 3,3 ', 4,4.
It is possible to produce a multilayer polyimide film in which a base polyimide layer containing 4'-biphenyltetracarboxylic dianhydride and paraphenylenediamine as essential components and a flexible heat-fusible polyimide are laminated with a large peel strength.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C08L 79/08 C08L 79/08 Z // B29K 79:00 B29L 9:00

Claims (2)

[Claims] 1. An extruder having a two- or three-layer die for extruding a polyamic acid solution for a base layer and a solution of polyimide or a precursor thereof for a thin layer, and a solution casting film forming apparatus. In a method for producing a multilayer extruded polyimide film by a combined multilayer extrusion casting film forming method, a polyamic acid solution that gives a substrate polyimide (X) having an imide unit of the following formula is used as a polyamic acid solution for a substrate layer, Embedded image A solution of polyimide or a precursor thereof for a thin layer comprises the following imide units (A) and (B): [In the formula (B), R represents a tetravalent aromatic residue, and R ′ represents a divalent aromatic or aliphatic residue. (A) is 80 to 100 mol%, and (B) is 20 to 0 mol%.
A multi-layer extrudate containing a solvent extruded on a support is heated and dried and imidated using a solution of polyimide (Y) or a precursor thereof, which has a coefficient of linear thermal expansion of 5 × 10 ^{− 6 -30 × 10 -6 cm / cm} / ℃ a method of multilayer extrusion polyimide film. 2. Drying and imidizing polyimide (Y)
The method for producing a multilayer extruded polyimide film according to claim 1, wherein the heating is performed to a temperature not lower than the glass transition temperature and not higher than the deterioration temperature.